Updating HDFS to use CHPL_AUXIO_INCLUDE and CHPL_AUXIO_LIBS

Changing HDFS to use CHPL_AUXIO_INCLUDE and CHPL_AUXIO_LIBS for library and include paths. Updating README.hdfs to reflect this as well.
I think if you set CHPL_AUXIO_INCLUDE with ?= in runtime/etc/Makefile.auxFilesys this #ifdef can go away.